False “AP offline” messages from cloud manager

hi,lately (since about 6 weeks ago, after I disconnected 5-aps) I began to get many false email messages over one or few ap’s that are offline while every time I look via the cloud Mgr interface they seem to be working fine. Moreover I do not get from my clients location any call claiming that something is wrong with their WiFi..I guess those are all false messages ad I wonder to the cause of it?